1. Field of the Invention:
This invention relates to combined brake and steering hydraulic systems for vehicles having hydraulic brakes and hydraulic steering, and is particularly advantageous for articulated vehicles which require a relatively large flow of hydraulic fluid in the operation of the steering mechanism.
2. Description of the Prior Art:
Articulated vehicles, as referred to herein, comprise two separate frame portions, with the two frame portions connected by a combined draft and steering coupling. In order to steer such a vehicle it is necessary to turn one frame portion with respect to the other and this is commonly done by means of hydraulic actuators or jacks connected between the two frame portions.
Various kinds of brakes have been used for such vehicles, including pneumatic, combined pneumatic and hydraulic, full hydraulic and others. It is advantageous for many such vehicles to utilize hydraulic brakes and to employ a combined hydraulic steering and braking system.
In larger articulated vehicles it is common to utilize separate pumps to supply the steering system and the braking system, and it is known also to utilize three pumps, with the third pump arranged to be shifted between the steering and braking systems under various operating conditions.
For smaller articulated vehicles particularly it is advantageous to be able to utilize a single hydraulic pump to supply both the braking and steering systems, and the object of the present invention is to provide an improved system of this type.